This invention relates to pipe couplings and more particularly to pipe couplings of the kind adapted to connect together a plain ended pipe to another pipe. It is to be understood that the expression "pipe" as used herein includes pipes and tubes as such and also pipe-like members and fittings for use in pipework such as bends, elbows, "T" connectors, flange adaptors and parts and devices adapted to be fitted to pipework such as valves and pumps. Such pipes may have a variety of end configurations, and may, for example, be plain ended or flange ended. Pipe couplings of the kind referred to above commonly comprise an annular sleeve member for overlying the end of the plain ended pipe, a sealing gasket disposed in use in an annular disposition at one end of the sleeve member about the plain ended pipe, an annular compression flange disposed at the one end of the sleeve and arranged to be drawn axially against the sealing gasket by tightening means to cause the sealing gasket to be forced into sealing contact between the sleeve member and the outer periphery of the plain ended pipe located within the sleeve. Such pipe couplings can be formed, for example, predominantly of malleable iron, steel, or plastics material, the gaskets being of an appropriate elastomeric material.
Pipe couplings of this kind are often used for connecting two abutting plain ended pipes, in which case sealing gaskets and compression flanges are provided at both ends of the sleeve member, and tightening means usually connect between the two flanges. Commonly, such pipes are two pipes as such or a pipe and the plain end of a flange adaptor, for example.
The pairs of compression flanges for such couplings may be provided with tightening means connecting together the flanges and may comprise bolts passing along the length of the sleeve and through apertures spaced around the outer radially extremities of the flanges, such bolts being provided with a head at one end and carrying a nut at the other so that the flanges are drawn together by tightening the nuts on the bolts. Alternatively, the compression flanges may screw into or onto the ends of the sleeve.
Whilst such pipe couplings are widely used, historically a particular size coupling was only capable of dealing with a limited outside diameter range of plain ended pipes because of the constraints imposed by the use of an axially movable annular compression flange to compress the annular sealing gasket between the inner peripheral wall of the sleeve and the outer peripheral wall of the plain ended pipe to be connected and sealed by means of the coupling.
Attempts have been made to increase the range of pipes capable of being connected by individual couplings by coupling designs having annular gaskets of substantial gasket volume such that upon axial compression thereof, substantial radial distortion and expansion can occur so as to span an annulus of significant size between the interior of the coupling and the pipe to be sealed and connected thereby. However, constraints of cost on the volume of gasket used, and limits on reasonable possible compressive forces applicable on the gaskets still provide a significant restriction on the range of pipe sizes that can be accommodated by any one coupling whilst there is an ever increasing demand for such couplings for use with a wider size range of pipes. In addition technical problems arise in a tendency during axial compression for uneven axial movement of the sealing gasket and hence of the flange, about the pipe axis which can lead to serious jointing and sealing weakness.
It is an object of the present invention to overcome or at least substantially reduce the above-mentioned problems.